1. Field of the Invention
The present invention relates to thin film heads for magnetically writing information on data storage media, and particularly to fabrication processes for manufacturing such heads. Still more particularly, the invention concerns the reduction of write head feature size beyond that which can be achieved using conventional photolithography.
2. Description of the Prior Art
By way of background, thin film magnetic write heads for use in data storage devices, such as disk drives, conventionally include P1 and P2 pole pieces that cooperate to record magnetic domains in concentric track patterns on an underlying data storage medium. The configuration of such pole pieces, and particularly the track width feature size, is an important determinant of the track width of the magnetic domains recorded on the underlying medium. Because narrow track width translates to increased data storage capacity, all other things being equal, it is a design goal of disk drive manufactures to reduce the track width feature size of the pole pieces.
In thin film magnetic head processing, features are constructed using photolithographic processes. For example, to fabricate a pole piece, a photoresist layer is formed, then photo-exposed using a photolithographic mask to define the pole piece geometry and then photo-developed to form a trench conforming to the defined geometry. The metallic pole piece material (typically a nickel-iron alloy) is deposited in the trench using an electroplating process. The remaining photoresist material is then stripped away, leaving behind the fully formed pole piece.
The problem with this type of processing is that feature size can only be narrowed photolithographically by using shorter wavelength light and contrast enhancement techniques. Thus, whether conventional photolithography is used, or newer technologies such as deep UV or electron beam lithography, reductions in feature size typically require new and more expensive light sources and exposure technology. An additional disadvantage of photolithographic solutions is that line edge roughness becomes a concern as photolithographic features become ever smaller.
Accordingly, an improved technique for reducing feature size in a thin film magnetic write head is required if improvements in disk drive performance are to be achieved. What is particularly needed is a new technique whereby pole piece feature size can be reduced while using any thin film magnetic head photolithographic process, including deep UV or electron beam lithography, without having to resort to expensive photolithographic resolution enhancement solutions. An additional requirement is that the technique be compatible with the low melting point of conventional photoresist materials and with the low temperature processing restrictions that apply to the fabrication of integrated read/write heads, wherein a magnetic write head is combined with a thin film magnetic read head. Elevated processing temperatures in such environments can damage the read head elements, which are typically comprised of extremely thin ferromagnetic layers. A further requirement is that of reducing the line edge roughness of the photolithographically defined trenches.